US5521642A - Decoding system for compact high definition television receivers - Google Patents

Decoding system for compact high definition television receivers Download PDF

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US5521642A
US5521642A US08/133,663 US13366393A US5521642A US 5521642 A US5521642 A US 5521642A US 13366393 A US13366393 A US 13366393A US 5521642 A US5521642 A US 5521642A
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frame
reduced
pixel
data
motion vector
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Hak-Jae Park
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Quarterhill Inc
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Daewoo Electronics Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/015—High-definition television systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/59—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
    • H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding

Definitions

  • the present invention relates to a digital image decoder for use in a high definition television receiver; and, more particularly, to a digital image decoder for a compact-sized high difinition television receiver having a small-sized screen through the use of d.c. transform coefficients.
  • Transmission of digitized television signals makes it possible to deliver video images of a much higher quality than that of analog signals.
  • an image signal comprising a sequence of image "frames"
  • a substantial amount of data need be transmitted, especially in the case of high defition television (HDTV) system.
  • HDTV high defition television
  • the available frequency bandwidth of a conventional transmission channel is limited, in order to transmit substantial amounts of digital data, e.g., about 900 Mbits per second, through the limited channel bandwidth, e.g., of 6 MHz, it is inevitable to compress the image signal.
  • hybrid coding technique which combines spatial and temporal compression techniques, is known in the art to be most effective.
  • the motion-compensated DPCM is a process of determining the movement of an object between a block of a current frame and a corresponding block of its previous frame, and predicting the current frame according to the motion flow to produce a predictive error signal representing the difference between the current frame and its prediction.
  • the two-dimensional DCT converts a block of digital image signal, for example, a block of 8 ⁇ 8 pixels, into a set of transform coefficients.
  • This technique is described in Chen and Pratt, "Scene Adaptive Coder", IEEE Transactions on Communications, COM-32, No. 3(March 1984).
  • the transform coefficients the one which represents the average value of the pixels in a block is called a d.c. coefficient.
  • This coefficient carries the greatest share of the energy in the transform domain; and the remaining transform coefficients, which all represent zero mean, are called a.c. coefficients.
  • the motion vectors obtained by the motion-compensated DPCM are also coded by VLC.
  • a conventional decoding system incorporated in a HDTV receiver employing a hybrid coding technique, which includes: a variable length decoder 12, a run-length decoder 14, an inverse zigzag scanner 16, an inverse quantizer 18, an inverse DCT means 20, a frame memory 22 for storing previous frame data, a motion compensator 24 and an adder 28 for generating current block data from the previous frame data, and motion vector and prediction error data.
  • a hybrid coding technique which includes: a variable length decoder 12, a run-length decoder 14, an inverse zigzag scanner 16, an inverse quantizer 18, an inverse DCT means 20, a frame memory 22 for storing previous frame data, a motion compensator 24 and an adder 28 for generating current block data from the previous frame data, and motion vector and prediction error data.
  • an object of the present invention to provide a simplified decoding system adapted for use in a compact-sized HDTV receiver.
  • Another object of the present invention is to provide a simplified decoding system capable of providing a small size picture suitable for a compact HDTV receiver.
  • a simplified decoding system which is capable of providing a reduced image frame to a compact-sized HDTV receiver with a small size screen through the use of d.c. transform coefficients.
  • the decoding system selectively decodes and inversely quantizes d.c. transform coefficients only so as to produce a set of difference data, each of which represents an average of pixel difference values between a block of two-dimensional pixels of a current frame and a corresponding block of its preceding frame.
  • Each of the two-dimensional motion vectors is also decoded and modified to compensate the reduced image frame and to derive a pixel data from the previous reduced frame based on the modified motion vector.
  • the derived pixel data and the average pixel difference data are combined so as to generate the reduced frame.
  • FIG. 1 shows a block diagram of a conventional decoding system utilized in a HDTV receiver
  • FIG. 2 is a block diagram of a simplified decoding system adapted for use in a compact-sized HDTV receiver in accordance with the present invention.
  • FIG. 3 explains the motion prediction and interpolation performed in the decoding system as shown in FIG. 2 for generating a reduced size picture in accordance with the invention.
  • FIG. 2 there is shown a block diagram schematically illustrating a decoding system 100 for providing reduced size pictures to a compact-sized HDTV receiver.
  • a sequence of encoded digital signals is inputted to the decoding system 100.
  • Each of the input signals includes a set of variable length coded transform coefficients which have been encoded from the difference values between a block of two-dimensional pixels of a current frame and a corresponding block of its preceding frame after motion compensation and a variable length coded two-dimensional motion vector data which represents a motion displacement between the two blocks.
  • a variable length decoder (VLD) 31 decodes the set of variable length coded transform coefficients and the motion vectors to send the transform coefficient data to an inverse quantizer Q -1 33 and the motion vector data to a motion compensator 35.
  • the VLD 31 is basically a look-up table: that is, in the VLD 31, a plurality of code sets is provided to define respective relationships between variable length codes and their run-length codes or motion vectors.
  • the VLD 31 not all of the variable length coded transform coefficients in a set are decoded, but a first one of them is selectively decoded to generate a quantized DCT coefficient.
  • the quantized DCT coefficient corresponds to a d.c. coefficient among a set of DCT coefficients which would have been generated through their conversion by using such means as a run-length decoder and a zigzag scanner.
  • the inverse quantizer Q -1 33 converts the d.c. coefficient into a difference data which represents an average of pixel difference values between a given block of two-dimensional pixels of the current frame and its corresponding block of the previous frame. And then, the average pixel difference data is supplied to an adder 37 to form an image frame.
  • the DCT transform coefficients have a ststistic distribution in the frequency region between a d.c. component zone to a high frequency zone with non-zero or significant transform coefficients mainly appearing in the low frequency zone and the zero or insignificant transform coefficients appearing mainly in the high frequency zone.
  • These high frequency components may be truncated or do not have to be utilized in generating images of a reduced size. Accordigly, it may be possible to utilize the lower frequency zone only to reproduce a reduced size picture.
  • a d.c. coefficient is utilized in producing a reduced size picture.
  • each of the pixels is converted into a set of DCT coefficients before being transmitted to the receiver.
  • the d.c. coefficient in the set of the DCT coefficients is the one having the average value of the 64 pixels in the block. Therefore, it will be appreciated that each of the d.c. coefficients having the average values can be used to produce a representative signal of the blocks constituting the current frame, capable of producing a reduced size picture.
  • the d.c. coefficients are utilized to produce the reduced size picture, such processes as run-length decoding, inverse zigzag scanning and inverse discrete cosine transform are not required and thus a desired simplified decoding system is achieved.
  • variable length decoded motion vector from the VLD 31 is fed to the motion compensator 35.
  • N e.g. 8
  • the motion vector specifically, the horizontal vector component MVH and the vertical vector component MVV from the VLD 31, are also reduced in their horizontal and vertical lengths to compensate the reduced size picture.
  • the motion compensator 35 performs to divide or reduce the horizontal vector component and the vertical vector component by a predetermined factor N, e.g., 8, respectively, which are then fed to an interpolator 41.
  • the interpolator 41 extracts a corresponding pixel data from the previous frame stored in a frame memory 39 based on the motion vector reduced by the factor of, e.g., 8 in the motion compensater 35 and applies the corresponding pixel data to the adder 37.
  • the corresponding pixel data derived from the interpolator 41 and the average pixel difference data from the inverse quantizer Q -1 33 are summed up at the adder 37 to constitute a representative image data of a given block of the current frame and written onto the frame memory 39.
  • the reduced motion vector from the motion compensater 35 does not always coincide with the pixel position of the previous frame stored in the frame memory 39; and, therefore, a pixel data of the previous frame is interpolated, in accordance with the invention, by using the interpolator 41 and then applied to the adder 37. Details of the interpolation process will be described hereinafter with reference to FIG. 3.
  • the average pixel difference data from the inverse quantizer Q -1 33 and the interpolated pixel data from the interpolator 41 are added up to provide a representative image data for a block of 8 ⁇ 8 pixels in the current frame.
  • the representative image data is successively stored in the frame memory 39 so as to generate the reduced image frame for display.
  • FIG. 3 there is illustrated a spatial relationship between a pixel of a reduced current frame and pixels on its preceding frame operated by a reduced motion vector MV/N.
  • a motion vector operates from a base, which is a current pixel projected on its preceding frame, to a head which is a pixel in the preceding frame.
  • B, P, Q, R, S, T, U, V and W are pixels on the preceding frame denoted by closed circles; and open circles signify the base B and the heads Hi's.
  • Each of the pixel data of such heads that fall on a vertical or horizontal line which connects pixels, e.g., H3 or H4, is derived from its two neighboring pixels on the line by multiplying appropriate weight factors thereto.
  • H3 is derived from S and T; and H4, from U and V.
  • the pixel data thereof is interpolated from those four pixels by applying suitable weight factors thereto.
  • the pixel data of H2 for instance, is derived from P, Q, R and S.
  • the weight factors are determined based on the reversed ratio of distances between the head of a reduced motion vector and its two or four neighboring pixels.
  • the interpolated pixel data DH3 for head H3 is obtained by summing up the pixel data DS of S multiplied by a weight factor of TH3/(SH3+TH3) and the pixel data DT of T multiplied by a weight factor of SH3/(SH3+TH3), wherein SH3 is the distance between S and H3 and TH3 being the distance between T and H3.
  • SH3 is the distance between S and H3 and TH3 being the distance between T and H3.
  • the interpolated pixel data DH2 for head H2 is obtained by multiplying(PH2+QH2+RH2+SH2) -1 to the sum of DP ⁇ SH2, DQ ⁇ RH2, DR ⁇ QH2 and DS ⁇ PH2, wherein DP, DQ, DR and DS are pixel data of P, Q, R and S, respectively, and PH2, QH2, RH2 and SH2 represent the distances between H2 and P, Q, R and S, respectively, with PH2>QH2>RH2> SH2.
  • the reduced motion vector by a factor of N is fed from the motion compensator 35 to the interpolator 41 wherein the aforementioned interpolation process is performed.
  • the interpolated pixel data from the interpolator 41 is added to the average pixel difference data from the inverse quantizer Q -1 33 at the adder 37 and written onto the frame memory 39 for storing the reduced image signal.
  • the novel decoding system which is capable of providing compact HDTV receivers with small size pictures, wherein the generation of the small size pictures is achieved by using d.c. coefficients alone, thereby eliminating the need to employ a complicated and costly decoder or decoding process, and enabling the adaptation of a simplified decoding system.
  • weight factors which are employed to carry out the interpolation of a pixel data and inversely proportional to the distances between a given head and its two or four nearest pixels in accordance with the preferred embodiment of the invention, may be chosen in different manners: for instance, they may be chosen to be inversely proportional to the square of the ratio of distances as long as use of such weight factors turns out to be more conducive to the reproduction of better pictures.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)
  • Television Systems (AREA)
US08/133,663 1992-10-07 1993-10-07 Decoding system for compact high definition television receivers Expired - Lifetime US5521642A (en)

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KR1019920018394A KR970000761B1 (ko) 1992-10-07 1992-10-07 소형 디지탈 방식 고선명 텔레비젼
KR92-18394 1992-10-07

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Cited By (8)

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EP0993198A2 (en) * 1998-10-09 2000-04-12 Matsushita Electric Industrial Co., Ltd. Efficient down conversion system for 2:1 decimation of a video signal
EP1103918A2 (en) * 1999-11-24 2001-05-30 Xerox Corporation Image enhancement on JPEG compressed image data
US6310982B1 (en) * 1998-11-12 2001-10-30 Oec Medical Systems, Inc. Method and apparatus for reducing motion artifacts and noise in video image processing
WO2003026296A1 (en) 2001-09-17 2003-03-27 Nokia Corporation Method for sub-pixel value interpolation
US20030068087A1 (en) * 2001-10-05 2003-04-10 Watson Wu System and method for generating a character thumbnail sequence
US20040252895A1 (en) * 2003-06-16 2004-12-16 Hur Bong-Soo Pixel-data selection device to provide motion compensation, and a method thereof
AU2007237319B2 (en) * 2001-09-17 2011-01-20 Nokia Technologies Oy Method for sub-pixel value interpolation
KR101091217B1 (ko) 2003-12-10 2011-12-07 소니 주식회사 화상 처리 방법 및 장치, 및 컴퓨터 판독가능 기록매체

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Cited By (24)

* Cited by examiner, † Cited by third party
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EP0993198A3 (en) * 1998-10-09 2001-01-31 Matsushita Electric Industrial Co., Ltd. Efficient down conversion system for 2:1 decimation of a video signal
KR100707116B1 (ko) 1998-10-09 2007-04-16 마쯔시다덴기산교 가부시키가이샤 2:1 데이메이션을 위한 효율적인 다운변환 시스템
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US6310982B1 (en) * 1998-11-12 2001-10-30 Oec Medical Systems, Inc. Method and apparatus for reducing motion artifacts and noise in video image processing
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WO2003026296A1 (en) 2001-09-17 2003-03-27 Nokia Corporation Method for sub-pixel value interpolation
CN1331353C (zh) * 2001-09-17 2007-08-08 诺基亚有限公司 用于子像素值内插的方法
AU2002324085B2 (en) * 2001-09-17 2007-09-06 Nokia Technologies Oy Method for sub-pixel value interpolation
US7280599B2 (en) 2001-09-17 2007-10-09 Nokia Corporation Method for sub-pixel value interpolation
AU2007237319B2 (en) * 2001-09-17 2011-01-20 Nokia Technologies Oy Method for sub-pixel value interpolation
US20030112864A1 (en) * 2001-09-17 2003-06-19 Marta Karczewicz Method for sub-pixel value interpolation
AU2002324085C1 (en) * 2001-09-17 2008-06-05 Nokia Technologies Oy Method for sub-pixel value interpolation
US20030068087A1 (en) * 2001-10-05 2003-04-10 Watson Wu System and method for generating a character thumbnail sequence
US7336838B2 (en) * 2003-06-16 2008-02-26 Samsung Electronics Co., Ltd. Pixel-data selection device to provide motion compensation, and a method thereof
US20040252895A1 (en) * 2003-06-16 2004-12-16 Hur Bong-Soo Pixel-data selection device to provide motion compensation, and a method thereof
KR101091217B1 (ko) 2003-12-10 2011-12-07 소니 주식회사 화상 처리 방법 및 장치, 및 컴퓨터 판독가능 기록매체

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JPH06209456A (ja) 1994-07-26
KR970000761B1 (ko) 1997-01-18
KR940010779A (ko) 1994-05-26

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